Method of treating sewing thread and the thread resulting therefrom



Sept. 26, 1939. BURGEN] 2,173,997

METHOD OF TREATING SEWING THREAD AND THE THREAD RESULTING THEREFROMFiled Feb. 21, 1939 I x 5 I INVENT OR. 5 .ZZf/"d fiuiyelzz PatentedSept. 26, 1939 UNITED STATES PATENT OFFICE METHOD OF TREATING SEWINGTHREAD AND THE THREAD RESULTING THERE- FROM Application February 21,1939, Serial No. 257,566

17 Claims.

This invention relates to a novel and improved method of treatingsewingthread and to the thread resulting therefrom. The novel features of themethod and thread will be best understood from the following descriptionand the annexed drawing, in which I have shown selected types ofapparatus with which the method may be practiced and in which:

Fig. 1 is a diagrammatic viewof an apparatus which may be used in thepractice of the method;

Fig. 2 is a view similar to Fig. 1, but showing part of an apparatuswhich may be used in the practice of the invention according to asomewhat diiferent method;

Fig. 3 is a diagrammatic view of an apparatus which may be used inconjunction with the apparatus of Fig. 2.

Primarily, my invention relates to the manufacture of thread of what forthe sake of con- 20 venience I may call native cellulosic fibers, bywhich I mean natural unmercerized vegetable fibers such as cotton,linen, jute, ramie, etc., which still have substantially their nativechemical composition and native crystal structure, except 'as -thatcomposition and structure may be affected by this invention. By the termsewing thread I refer to any thread or yarn or part thereof wherein thetensile strength of the thread is determined largely by the strength ofthe fibers 30 rather than by the amount of friction tending to holdtogether the individual fibers.

Since the invention is of particular value in connection with cottonfibers, I shall assume in the following description that cotton is thema- 35 terial of the thread being treated.

In the practice of my invention, I first thoroughly saturate the thread,preferably with water, and then while the thread is thus saturated, Istretch it, preferably beyond its elastic limit 40 but short of itsbreaking point. The stretching can be measured by the amount ofelongation of the thread, and this elongation under the above stretchingaction is preferably greater than 50% of the maximum elongation whichcan occur in 45 the thread without breaking. As a matter of fact, thestretching is preferably carried as near to the breaking point aspractical without causing actual in the sewing properties to which Irefer are an 1 increased tensile strength, a uniformity of tensilestrength for a wide range of humidity, a prevention of kinking, and amore compact structure and smoothness of yarn or thread.

Referring now to the drawings, and first to Fig. 1, the threads I may bepassed under guides 2 in a tank 3 containing a suitable liquid 4 inwhich the threads are saturated, and then they are passed between a setof rollers 5 and thence to a second set of rollers 6, the rollers 5rotating at a slower speed than the rollers 6 so as to stretch thethread at I therebetween, to the extent stated above.

After the thread has left the rollers 6, of course the stretchingtension exerted by the rollers 5 and 6 is released, although it maystill be under some tension if it is to be wound or possibly if it is tobe handled in some other operation. However, the stretching tension isreduced to a very substantial amount. Then the thread may be, andpreferably is, subjected to a second wetting operation. This operationmay be performed by any suitable apparatus and in any suitable manner,the details of which may vary widely. After the second wetting, thethread may then be dried.

The liquid used for the second wetting operation is preferably of thesame character as the liquid 4 and in any case is preferably not a,weaker swelling agent than the liquid 4. When treating cotton, both ofthese liquids may conveniently be water, which is known as a relativelystrong swelling agent, either in liquid or vapor form, although I mayuse other agents having the property of swelling native cellulose fiberswithout substantially changing their native structure. The liquid usedshould not materially change the chemical composition of the fibers,leaving them in substantially their native state. The temperature of theliquids may vary widely for different working conditions'but ispreferably room temperature or higher. Ofcourse, when water vapor isused, the temperature willbe much higher than that of a room. As amatter of convenience,

it is desirable to perform the initial wetting and stretching operationsprior to bleaching or dyeing, in which case the bleaching or dyeingoperation may be used also as the second wetting step of the process.

The result of the treatment described above is a thread which hasgreatly improved sewing qualities and in which those qualities aresubstantially uniform throughout a wide range of humidity. This isparticularly true as to tensile strength. For example, I have foundthat, between 21 and 60 relative humidity, which may be considered as anormal range, the variation in strength with thread treated according tomy invention is on the order of about 4% as compared with a variation onthe order of 14% for the same range of relative humidity with thread nottreated according to the invention.

Likewise, I have found that if the method described above is combinedwith a mercerizing treatment, the strength and luster of the thread bothare greatly increased beyond what is obtained by mercerizing alone,although after mercerizing, the fibers are no longer in their nativestate. Preferably, the wetting and stretching are done beforemercerizing.

Probably the correct explanation of the improved results is as follows:

The breaking load of sewing thread, which usually is made up of severalsingle strands twisted together, is determined principally by thestrength of the individual fibers of which the strands consist. Thesefibers, which it is assumed are native cellulosic fibers, are swollen bythe first wetting operation described above and then the subsequentstretching of the swollen fibers results in what is known as plasticdeformation of the fibers. This plastic deformation is caused by arearrangement of the micellae of which the fibers consist. By thisrearrangement the micellae of any one fiber acquire a greaterparallelism to the axis of that fiber than before and the cohesion ofthe micellae or their attraction for each other is increased, resultingin an increase in fiber strength.

It is also possible that the methods described above may decrease thefiber slippage in some threads, thereby also increasing the strength ofthe thread.

Similarly, the plastic deformation results in an equalization orsubstantial uniformity of thread strength throughout the normal range ofatmospheric humidity. This fact may be understood by considering theprocess of breaking thread, for example in a strength testing machine.When thread is thus broken, that breaking is accompanied and materiallyinfluenced by the plastic deformation of the fibers, because theatmospheric moisture acts as a swelling agent, loosening the forces ofattraction between the micellae of the individual fibers and therebydecreasing the fiber strength. At the same time, however, the micellaeof the swollen fibers become more freely movable and, under the stressapplied in the testing machine, plastic deformation takes place,bringing the micellae of each fiber into a state of greater parallelismwith respect to the fiber axis, thereby strengthening the fiber. As willbe readily seen, these two phenomena counteract each other with regardto strength. The swelling in humid air causes a decrease of cohesion;whereas the rearrangement of the micellae improves that cohesion. Rayon,for instance, which has a highly pronounced tendency to swell in watershows a decrease of strength with increased atmospheric humidity;whereas cotton and other native fibers, which swell to a lesser degree,show increased fiber strength with increasing humidity.

For example, in a sewing thread made of cotton fibers, previouslysubjected to wet stretching according to this invention, the greatercohesion of the micellae caused by atmospheric humidity is essentiallyanticipated. Therefore, when a thread has been thus treated is subjectedto a relatively high atmospheric humidity, that humidity is of littlehelp in further increasing the strength of the thread. For example, if athread of cotton fibers which has been previously wet stretchedaccording to this invention is loaded up to the breaking point in arelatively high atmospheric humidity, this repetition of wet stretchingdoes not help materially to change the structure of the individualfibers beyond what has already been accomplished. That is, the plasticdeformation is substantially completed by treatment according to myinvention. For the same reason dry air does not decrease the strength ofyarn which has been wet stretched according to this invention, since thedesired plastic deformation of the fibers has previously taken place.

However, thread of cotton fibers which has not been treated according tothis invention shows considerably higher tensile strength when broken inhumid atmosphere than when broken in relatively dry atmosphere, probablybecause breaking the thread in humid atmosphere results in the plasticdeformation, as noted above.

Therefore a convenient test for thread, to determine whether or not ithas been treated according to the invention, is to test it for itstensile strength and then submit it to a thorough wetting and subsequentstretching and then test it again for tensile strength. Sewing threadwhich has been treated according to my invention will show no apreciableincrease in strength,

whereas sewing thread which has not been so treated will now show adecided increase in strength, as will be seen from the examples givenbelow.

The, treatment may be carried on with the thread at various stages inits manufacture. Bleached thread is more easily penetrated by the wateror other wetting agent and so it often is convenient to practice theinvention with thread in that condition. When grey thread is used,preferably an appropriate wetting-out agent is employed to aid theswelling agent in entering the thread.

While I have shown in the drawing that the stretching is done in onestep, nevertheless under some conditions it is found that better resultsare obtained by carrying on the stretching in successive steps.

While the above is believed to be an adequate disclosure of theinvention, I shall give examples of treatments and the tests followingthose treatments. In these tests, the total strength of the thread ineach instance was determined in the usual way, by multiplying thebreaking strength of the thread by the yarn size thereof. The increasein strength caused by the treatment was measured by comparing thetreated threads with identical threads which had not been so treated. Itwas found that the increase in total yarn or thread strength is onlypartly due to the increased fineness of the thread caused by thetreatment, but is largely due to an actual increase in breaking strengthof the thread caused by the treatment. v

Examples (1). Grey 6/cord cotton threads of different counts weresaturated in water containing a known wetting-out agent to facilitatepenetration of the water. The threads were then stretched betweenrollers to a point approaching the breaking point of the thread. Thecoarser counts of thread take a higher stretch than the finer counts.For example, 46 6/cord thread was run through the method continuouslywithout breakage when given a stretch of 10.5% of its length. On theother hand, under similar conditions 1.5% was the limitofstretch givento 110 6/cord thread. After stretching, the thread was bleached anddried according to standard practice, in which of course the thread isreleased from the tension placed on it as described above, and thestrength and size of the resulting threads were subsequently tested at60 R. H. It was found that the total strengths of the threads hadincreased from 8% to 12%.

(2). Grey 36 2/cord thread was wet and stretched 6%, after which it wasbleached and dried, the-bleaching being used as the second wettingoperation. It was found that the strength of the thread had increased20% and its size had become 2.5% finer.

(3). Grey 60 3/cord thread was treated in the same manner as describedin Example 2 except that it was stretched 6 /2%, after which it wasbleached and dried, and it was found that its strength had increased 12%and its size had become 3.4% finer.

To show the relative uniformity of the tensile strength of the threadstreated according to this invention, the following data were obtainedfrom a test of a grey 46 6/cord thread which had been treated in themanner followed in Example 1, that is, it had been wet stretchedapproximately 10.5% and then bleached and dried. The thread was thentested at 60 R. H. and at 21 R. H., and in both instances the resultswere compared with similar tests on an untreated control sample. Theresults are given below, the size being measured in yards per pound, asknown in the art. t

Tensile strength of control sample at 60 Strength difference betweenstretched and unstretched thread measured at 60 humidity consideringattenuation of thread per cent Strength diiference between stretched andunstretched thread measured at 21 humidity considering attenuation ofthread per cent 22 Loss of thread strength of unstretched thread at 21humidity per cent 13.7

Loss of thread strength of stretched thread at 21 humidity "per cent 4.4

Referring now to Figs. 2 and 3, I have shown in Fig. 2 certain apparatusand other parts which are identical in function with those shown in Fig.1 and which are identified by the same numerals and therefore will notbe described further. In this figure, however, the threads, afterleaving the rollers 6, are shown as being wound upon a beam 8 and thiswinding is preferably done under such a relatively high tension as topreserve the stretch just given to the thread between the rollers 5 and6 or, in other words, to preserve or to set the plastic deformationwhich has been occasioned by the wet stretching through which the threadhas just gone. Then the threads which are thus tightly wound on the beamare preferably subjected to a boiling, for example in water, after whichthey may be wound under relatively little tension on another beam 9,preferably passing through and being saturated by a liquid ill in a tankii disposed between the two beams. In other words, the threads are woundtight on the beam 8 and slack on the beam 9. After passing through theliquid Ill, the threads may be dried, either on the beam 9 or by anysuitable drying apparatus (not shown), before winding on that beam.

' All of the steps described above have been found to be valuable inimproving the sewing qualities of the thread, although it is to beunderstood that various changes in the steps and in their order may bemade and that certain steps may be omitted without departing from theinvention as defined in the appended claims.

This application is a continuation in part of my copending applications,Ser. No. 129,307, filed March 6, 1937 and Ser. No. 210,567, filed May28, 1938.

I claim:

1. The method of treating sewing thread of native cellulosic fiberswhich comprises thoroughly wetting the thread without substantiallychanging its chemical composition, then stretching the wet thread beyondits elastic limit and short of its breaking point, releasing the tensionon the thread, and drying it in its condition of released tension.

2. The method of treating sewing thread of native cellulosic fiberswhich comprises thoroughly wetting the thread without substantiallychanging its chemical composition, then stretching the wet thread beyondits elastic limit and short of its breaking point, releasing the tensionon the thread and wetting it again, and drying it in its condition ofreleased tension.

3. The method of treating sewing thread of native cellulosic fiberswhich comprises thoroughly wetting the thread without substantiallychanging its chemical composition, stretching the wet thread beyond itselastic limit and short of its breaking point, winding it under tension,wetting it again, and winding it under relatively little tension.

4. The method of treating sewing thread of native cellulosic fiberswhich comprises thoroughly wetting the thread without substantiallychanging its chemical composition, stretching the wet thread beyond itselastic limit and short of its breaking point, winding it under tension,and unwinding and rewinding it under relatively little tension whilewetting it a second time.

5. The method of treating sewing thread of native cellulosic fiberswhich comprises thorough- 1y wetting the thread without substantiallychanging its chemical composition, stretching the wet thread beyond itselastic limit and short of its breaking point, winding it under tension,wetting it again, releasing the tension on the thread, and drying it inits condition of released tension.

6. The method of treating sewing thread of native cellulosic fiberswhich comprises thoroughly wetting the thread without substantiallychanging its chemical composition, stretching the wet thread beyond itselastic limit and short of its breaking point, winding it under tension,and wetting it again while thus tightly wound.

7. The method of treating sewing thread of native cellulosic fiberswhich comprises thoroighly wetting the thread without substantiallychanging its chemical composition, stretching the wet thread beyond itselastic limit and short of its breaking point, winding it under tension,and boiling it while thus tightly wound.

8. The method of treating sewing thread of native cellulosic fiberswhich comprises thoroughly wetting the thread without substantiallychanging itschemical composition, stretching the wet thread beyond itselastic limit and short of its breaking point, winding it under tension,boiling it while thus tightly wound, releasing the tension on thethread, wetting it again, and drying it.

9. The method of treating sewing thread of native cellulosic fiberswhich comprises thoroughly wetting the thread without substantiallychanging its chemical composition, stretching the wet thread beyond itselastic limit and short of its breaking point, winding it under tension,boiling it while thus tightly wound, and unwinding and rewinding itunder relatively little tension while wetting it a second time, andfinally drying it.

10. The method of treating sewing thread of native cellulosic fiberswhich comprises thoroughly wetting the thread without substantiallychanging its chemical composition, stretching the wet thread beyond itselastic limit and short of its breaking point, releasing the tension onthe thread, and then mercerizing it in the usual way.

11. The method of treating sewing thread of cotton fibers whichcomprises thoroughly wetting the thread without substantially changingits chemical composition, then stretching the wet thread beyond itselastic limit and short of its breaking point, releasing the tension onthe thread, and drying it in its condition of released tension.

12. A sewing thread containing native cellulosic fibers, and made inaccordance with the method of claim 1.

13. A sewing thread containing cellulosic fibers, and made in accordancewith the method of claim 10.

14. A sewing thread of native cellulosic fibers plastically deformed torearrange the miscellae of the fibers so that the micellae of a fiberhave a relatively greater parallelism to the axis of that fiber and havea. greater cohesion than in the natural fiber, said thread havingsubstantially the same tensile strength, after being wet and stretched,as it had before such wetting and stretching.

15. A sewing thread of native cellulosic fibers plastically deformed torearrange the micellae of the fibers so that the micellae of a fiberhave a relatively greater parallelism to the axis of that fiber and havea greater cohesion than in the natural fiber, said thread having lessthan the normal amount of kinkiness at normal twist and also havingsubstantially uniform tensile strength over substantially the wholerange of atmospheric humidity.

16. A sewing thread of native cellulosic fibers plastically deformed torearrange the micellae of the fibers so that the micellae of a fiberhave a relatively greater parallelism to the axis of that fiber and havea greater cohesion than in the natural fiber, said thread havingsubstantially uniform tensile strength over substantially the wholenormal range of atmospheric humidity.

17. A sewing thread of native cellulosic fibers plastically deformed torearrange the micellae of the fibers so that the micellae of a fiberhave a relatively greater parallelism to the axis of that fiber and havea greater cohesion than in the natural fiber, said thread having lessthan the normal amount of kinkiness at normal twist.

ALFRED BURGENI.

